Methods and Devices for Prevention of Hypothermia in a Mammal During Prolonged Exposure to Extreme Cold

ABSTRACT

Methods and devices for preventing a change in the core body temperature of a mammal under cold conditions are provided. In the subject methods, a requirement for thermal energy input in said mammal is first detected. In response to the detection of this requirement for thermal energy input, a surface of a portion of the mammal is contacted with a warm temperature medium under negative pressure conditions for a period of time sufficient to introduce thermal energy into the core body of the mammal. The subject devices include at least a means for detecting a requirement for thermal energy input and a means for contacting a surface of the mammal with a warm temperature medium under negative pressure conditions. The subject methods and devices find use in a variety of applications, and are particularly suited for use in maintaining the core body temperature of a mammal substantially constant under cold conditions for an extended period of time.

CROSS-REFERENCE TO RELATED APPLICATIONS

Pursuant to 35 U.S.C. §119 (e), this application claims priority to thefiling date of the U.S. Provisional Patent Application Ser. No.60/210,664 filed Jun. 9, 2000; the disclosures of which are hereinincorporated by reference.

GOVERNMENT RIGHTS

This invention was made with Government support under contractNBCH1030020 awarded by The Department of the Interior, contractM67854-00-C-2144a, awarded by the Marine Corps Systems Command, andcontracts DAMD17-03-2-0029, W911NF-05-1-0548, W911NF-07-1-0098 awardedby The Department of the Army. The Government has certain rights in thisinvention.

INTRODUCTION

1. Field of the Invention

The field of this invention is core body energy regulation.

2. Background of the Invention

Prolonged exposure to cold environmental conditions for extended periodsof time can result in a condition known as hypothermia which canmanifest itself in a variety of symptoms. The onset of symptoms isusually slow; there is likely to be a gradual loss of mental acuity andphysical ability. The person experiencing hypothermia, in fact, may beunaware that he or she is in a state that requires emergency medicaltreatment. Symptoms include: apathy or lethargy, confusion, drowsiness,loss of coordination, pale and cold skin, shock, slowing of breathing,slurred speech, uncontrollable shivering, and weakness. As such,prolonged exposure to cold environmental conditions can result insignificant adverse physical and mental effects.

There are a number of situations where it is desirable for a person tobe exposed to cold environmental conditions for extended periods oftime. For example, there are professions which require individuals towork under cold conditions, where such professions include, but are notlimited to: professions that require prolonged time spent underwater,professions that require prolonged time spent outdoors in cold climates,and the like.

As such, there is great interest in the development of a technology thatcan maintain the core body temperature of a mammal at a substantiallyconstant value for prolonged periods of time under cold conditions. Ofparticular interest would be the development of such a technology thataccomplished the above results in a manner that was well-tolerated bythe host, e.g., in a non-invasive manner that did not substantiallyimpair the ability of the host to perform various tasks, e.g., workrelated tasks.

RELEVANT LITERATURE

-   U.S. Pat. No. 5,683,438. See also WO 98/40039. Also of interest are:    Soreide et al., “A non-invasive means to effectively restore    normothermia in cold stressed individuals: a preliminary report,” J.    Emerg. Med. (1999 July-August)17(4):725-30 and Grahn et al.,    “Recovery from mild hypothermia can be accelerated by mechanically    distending blood vessels in the hand,” J. Appl Physiol. (1998)    85(5):1643-8.

SUMMARY OF THE INVENTION

Methods and devices for preventing a change in the core body temperatureof a mammal under cold conditions are provided. In the subject methods,a requirement for thermal energy input in said mammal is first detected.In response to the detection of this requirement for thermal energyinput, a surface of a portion of the mammal is contacted with a warmtemperature medium under negative pressure conditions for a period oftime sufficient to introduce thermal energy into the core body of themammal. The subject devices include at least a means for detecting arequirement for thermal energy input and a means for contacting asurface of the mammal with a warm temperature medium under negativepressure conditions. The subject methods and devices find use in avariety of applications, and are particularly suited for use inmaintaining the core body temperature of a mammal substantially constantunder cold conditions for an extended period of time.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1 to 6 provide various views of a device that can be employed topractice to the subject methods.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

Methods and devices for preventing a change in the core body temperatureof a mammal under cold conditions are provided. In the subject methods,a requirement for thermal energy input in said mammal is first detected.In response to the detection of this requirement for thermal energyinput, a surface of a portion of the mammal is contacted with a warmtemperature medium under negative pressure conditions for a period oftime sufficient to introduce thermal energy into the core body of themammal. The subject devices include at least a means for detecting arequirement for thermal energy input and a means for contacting asurface of the mammal with a warm temperature medium under negativepressure conditions. The subject methods and devices find use in avariety of applications, and are particularly suited for use inmaintaining the core body temperature of a mammal substantially constantunder chronic exposure to cold conditions for an extended period oftime. In further describing the subject invention, the subject methodsand devices will be discussed in greater detail, followed by a review ofrepresentative applications in which the subject methods and devicesfind use.

Before the subject invention is described further, it is to beunderstood that the invention is not limited to the particularembodiments of the invention described below, as variations of theparticular embodiments may be made and still fall within the scope ofthe appended claims. It is also to be understood that the terminologyemployed is for the purpose of describing particular embodiments, and isnot intended to be limiting. Instead, the scope of the present inventionwill be established by the appended claims.

In this specification and the appended claims, the singular forms “a,”“an” and “the” include plural reference unless the context clearlydictates otherwise. Unless defined otherwise, all technical andscientific terms used herein have the same meaning as commonlyunderstood to one of ordinary skill in the art to which this inventionbelongs.

Methods

As summarized above, the subject invention provides methods forpreventing a change in the core body temperature of a mammal under coldconditions. More specifically, the subject methods prevent a significantdecrease in the core body temperature of a mammal from occurring undercold conditions. By “significant decrease” is meant a decrease in braintemperature of a magnitude of at least about 1, usually at least about1.5 and more usually at least about 2° C. In many embodiments, asdescribed in more detail below, the subject methods are methods ofmaintaining the core body temperature of a mammal at a substantiallyconstant value under cold conditions for an extended period of time. By“maintaining at a substantially constant value” is meant that the corebody temperature of the mammal does not vary during the extended periodof time by more than an insubstantial amount, where by “insubstantialamount” is meant an amount ranging from about 0.2 to 5.0, usually fromabout 0.5 to 4.0 and more usually from about 1.0 to 2.0° C. The subjectmethods are meant to be employed under cold environmental conditions. By“cold environmental” is meant conditions that produce hypothermia in amammal, i.e., hypothermia producing conditions, when a mammal is exposedto the conditions for at least about 5 min, usually at least about 60min. The temperature of the conditions may vary depending on the natureof the conditions, e.g. in air, underwater, etc., but will generally beless than about 30, usually less than about 25 and more usually lessthan about 20.

In practicing the subject methods, the first step is to detect arequirement in the mammal for input of thermal energy. Morespecifically, the first step is to detect a need in the mammal for aninput of thermal energy in order to prevent a decrease in the core bodytemperature of the mammal. This requirement for thermal energy input maybe detected using any convenient protocol. One convenient protocol is todetect a thermoregulatory error in the mammal. By thermoregulatory erroris meant an error in the thermoregulation of the mammal such thatvarious physiological changes occur in the mammal in response to theerror. The thermoregulatory error may be detected by detecting one ormore of the physiological changes associated with the error.Physiological changes of interest include: change in temperature,vasoconstriction, change in blood pressure, tremor activity, and thelike. Involved in this portion of the claimed methods is a dataprocessing step for processing the thermal energy requirement data andactivating the contact with the warm temperature medium in responsethereto (as described in greater detail below), e.g., a step of using acomputing means that controls the contact of the heat exchange surfacewith the warm temperature medium.

Following detection of the requirement for thermal energy input, thermalenergy is input into the core body of the mammal. By core body is meantthe internal body region or portion of the mammal, as opposed to thesurface of the mammal. In inputting or introducing thermal energy orheat into the core body of the mammal, a surface of the mammal iscontacted with a warm temperature medium under negative pressureconditions for a period of time sufficient to achieve the desired amountof heat introduction. The surface that is contacted with the warmtemperature medium is generally a heat exchange surface which acts as aheat exchange means between the core body and the environment of themammal. Heat exchange surfaces of interest with the subject methodsinclude those found in the various regions of the mammal, e.g., thearms, legs, palms, soles, head, face, ears, and the like.

By negative pressure conditions is meant a pressure lower than ambientpressure under the particular conditions in which the method isperformed, e.g., 1 ATM at sea level. The magnitude of the decrease inpressure from the ambient pressure under the negative pressureconditions is generally at least about 10 mmHg, usually at least about20 mmHg and more usually at least about 35 mmHg, where the magnitude ofthe decrease may be as great as 85 mmHg or greater, but typically doesnot exceed about 60 mmHg and usually does not exceed about 50 mmHg. Whenthe method is performed at or about sea level, the pressure under thenegative pressure conditions generally ranges from about 740 to 675mmHg, usually from about 730 to 700 mmHg and more usually from about 725to 710 mmHg.

As mentioned above, the surface of the mammal is contacted with a warmtemperature medium under the negative pressure conditions. By warmtemperature medium is meant a medium that has a temperature which issufficient to provide the requisite or desired core body thermal energyinput or introduction. The nature of the medium may vary, the mediumbeing a temperature controlled solid material, e.g., warming blanket; aliquid; or gas; depending on the particular device employed to practicethe subject methods. The temperature of the warm temperature medium mayvary. The warm temperature medium generally has a temperature rangingfrom about 40 to 52, usually from about 42 to 50 and more usually fromabout 44 to 48° C.

Contact is maintained for a period of time sufficient for the desiredamount of core body thermal energy input or introduction to occur. Assuch, contact is generally maintained for at least about 1 min, usuallyat least about 2 min and more usually at least about 3 min, wherecontact may be maintained for up to 10 hrs or longer, but is generallynot maintained for longer than 1 day and usually is not maintained forlonger than 1 hr.

In practicing the subject methods, the negative pressure conditionsduring contact may be static/constant or variable. Thus, in certainembodiments, the negative pressure is maintained at a constant valueduring contact of the surface with the low temperature medium. In yetother embodiments, the negative pressure value is varied during contact,e.g., oscillated. Where the negative pressure is varied or oscillated,the magnitude of the pressure change during a given period may be variedmay range from about −85 to 40 mmHg, usually from about −40 to 0 mmHg,with the periodicity of the oscillation ranging from about 0.25 sec to10 min, usually from about 1 sec to 10 sec.

In practicing the subject methods, the negative pressure conditions maybe provided using any convenient protocol. In many embodiments, thenegative pressure conditions are provided by enclosing a portion of themammal that includes the target surface that is to be contacted with thelow temperature medium in a sealed enclosure, where the pressure is thenreduced in the sealed enclosure thereby providing the requisite negativepressure conditions. The portion that is enclosed in the sealedenclosure is a portion of the mammal that includes the target heatexchange surface, and therefore is an appendage in many embodiments ofthe subject invention. As such, the portion that is sealed is an arm orleg, or at least a portion thereof, e.g., hand or foot, in manyembodiments of the subject invention. The nature of the enclosure willvary depending on the nature of the appendage to be enclosed, whererepresentative enclosures include gloves, shoes/boots, or sleeves, wherethe latter is described in greater detail supra in connection with thedescription of the representative devices that can be used to practicethe subject invention.

The magnitude of core body thermal energy introduction accomplishedduring practice of the methods may vary, and is sufficient to maintainthe core body temperature of the mammal at a substantially constantvalue. In many embodiments, the magnitude of heat introduction isgenerally at least about 0.5 Kcal/min, usually at least about 1 Kcal/minand more usually at least about 1.5 Kcal, where the magnitude may be asgreat as 50 Kcal/min or greater, but generally does not exceed about 30Kcal/min and usually does not exceed about 15 Kcal/min. The period oftime that the heat is introduced into the core body may vary, buttypically ranges from about 1 min to 24 hrs, usually from about 2 min to10 hrs and more usually from about 2 min to 5 hrs.

In the subject methods, the above described steps may be performed asingle time or a plurality of times over any given time period, i.e.,they may be performed once during a given time period or iterated 2 ormore times during a given time period. Where the above steps areperformed two or more times during a given time period or temporalduration, the multiple detecting steps may take the form of monitoringthe user during the time period in a substantially continuous manner,such that the requirement for thermal energy input is detected as afunction of time in a substantially continuous manner.

The subject methods are suitable for use with a variety of mammals.Mammals of interest include, but are not limited to: race animals, e.g.,horses, dogs, etc., work animals, e.g., horses, oxen etc., and humans.In most embodiments, the mammals on which the subject methods arepracticed are humans.

Devices

The above described methods may be practiced using any convenientdevice. In general, any device that is capable of: detecting a need forthermal energy input, achieving negative pressure and achieving warmtemperature medium contact with the target heat exchange surface for therequisite period of time may be employed. The devices employed in thesubject methods include a sensing element for detecting a requirementfor thermal energy input. This particular sensing element may varydepending on the how the requirement is detected. For example, where therequirement is detected by detecting a thermoregulatory error asmanifested by the appearance of vasoconstriction, a thermosensor findsuse. Other detection devices of interest include, but are not limitedto: pressure sensor, EMG, thermometer, and the like. The devices alsogenerally include a detection element for detecting when thermal energyinput is no longer required to maintain the core body temperature of themammal, where this detection element is often the same as the elementfor detecting the requirement for thermal energy input.

The subject devices also include a negative pressure element forproviding the negative pressure environment at the target heat exchangesurface. In many embodiments, this means for providing a negativepressure environment includes a sealing element for sealing an appendageof the mammal in an enclosed environment in which negative pressureconditions can be produced. Representative enclosing means or sealingelements include sleeves, boots/shoes, gloves, etc. which are inoperational relationship with a negative pressure inducing means, e.g.,a vacuum, that is capable of producing a negative pressure environment,as described above, in the sealed enclosure. The negative pressureinducing element may be actuated in a number of different ways,including through motor driven aspiration, through a system of valvesand pumps which are moved through movement of the mammal in a mannersufficient to create negative pressure in the sealed environment, etc.

As mentioned above, the subject devices also include an element forcontacting the heat exchange surface with the warm temperature medium.Representative means for contacting the surface with a warming mediuminclude: warming blankets, warm water immersion means, warming gasmeans, etc. In many embodiments, the device further includes a means forproducing the warm temperature medium, where this means may varydepending on the nature of the warm temperature medium. For example,where the warm temperature medium is a warming blanket whose temperatureis modulated by actuation of resistance heating elements in the blanket,this means for producing a warm temperature medium is a means forproviding electrical current to the warming blanket. Alternatively,where the warm temperature medium is a warm gas, e.g., air, the meansfor producing the warm medium is a means for warming or heating the gas,e.g. a microfurnace, and the like.

A representative device that can be readily adapted for use in thesubject methods is that described in U.S. Pat. No. 5,683,438, thedisclosure of which is herein incorporated by reference. In certainembodiments, the devices are adaptations of those devices described inU.S. patent application Ser. No. 09/839,590; the disclosure of which areherein incorporated by reference.

FIGS. 1 to 6 provide various views of another embodiment of a devicethat can be employed to practice the subject invention. The features ofthe system depicted in FIGS. 1 to 6, belonging to AVACore Technologies,Inc. (Palo Alto, Calif.), are preferred for carrying out themethodologies described herein. The system described includes a negativepressure chamber in which to apply or remove thermal energy from a humansubject. An improved interface between the chamber and its externalenvironment is provided.

Aquarius, Inc. (Scottsdale, Ariz.) produces a system that may be used orvariously modified for use in the stated method(s). However, that systemutilizes a “hard” seal interface with a user. The system describedherein may utilize a “soft” seal. A “hard” seal is characterized as onedesigned to altogether avoid air leakage past the boundary it provides.In theory, a “hard” seal will allow a single evacuation of the negativepressure chamber for use in the methods. In practice, however, a “hard”seal can produce a tourniquet effect. Also, any inability to maintain acomplete seal will be problematic in a system requiring as much.

A “soft” seal as described herein is characterized as providing anapproximate or imperfect seal at a user/seal interface. Such a seal maybe more compliant in its interface with a user. Indeed, in response touser movement, such a seal may leak or pass some air at the user/sealinterface. In a negative-pressure system designed for use with a softseal, a regulator or another feedback mechanism/routine will cause avacuum pump, generator, fan or any such other mechanism capable ofdrawing a vacuum to respond and evacuate such air as necessary tostabilize the pressure within the chamber, returning it to the desiredlevel. Active control of vacuum pressure in real-time or atpredetermined intervals in conjunction with a “soft” seal provides asignificant advantage over a “hard” seal system that relies on simplypulling a vacuum with the hopes of maintaining the same.

A further disadvantage over the Aquarius system has more to do with sealconfiguration than its barrier function. Entry and exit from theAquarius seal is difficult. Whether “hard” or “soft” in function, thepresent system provides a two-sided seal configuration. The meaning ofthis will be more apparent in view of the following figures anddescriptive text.

FIGS. 1 and 2 provide fore and aft perspective views of a negativepressure thermal exchange module (100). FIG. 3 provides an exploded viewof the same. The system components not shown in the figures include athermal control or perfusion unit. Such a unit may be adapted to providea stream of heat exchange media such as water at elevated temperatures,lowered temperatures or both. Further, a vacuum source and regulatoroptionally used with module (100) are not shown. Any sort of vacuumsource or regulator/control mechanism may be used with module (100) aswould be apparent to one with skill in the art. Together, thesecomponents work to maintain a pressure within module (100) during usebetween about 20 and 25 inches of H₂O and temperatures for core bodycooling between about 19 and 22° C. or temperatures for core bodyheating between about 40 and 45° C.

As shown, module (100) includes a housing (102) defining a negativepressure chamber (104), a heat-exchange element (106) and a soft,two-sided seal (108) supported by seal frame elements (110).

Housing (102) may be made from a cover (112) and a base (114). Negativepressure chamber (104) is preferably provided between heat exchangeelement (106) and cover (112). The embodiment shown is adapted to fitthe hand of a human user. Chamber (104) is preferably configured to fita human hand of any size. In order to provide a more space-efficientpackage, however, it may be more preferably sized to fit 95% of humanhand sizes. Alternately, it may be sized for more particularized groups,such as children. It is also contemplated that the housing may beconfigured to fit a human foot since the under surface of a foot mayalso be used effectively as a heat exchange surface.

Housing (102) may be constructed from multiple pieces, including an endcap (116) as shown, or it may be provided as a unitary structure. Cap(116) is shown including a ports (118). A first port may be utilized forconnection to a vacuum source, while the second may be utilized for avacuum gauge. Of course, alternate port placement is also possible.

Preferably, housing (102) is made of plastic. Most preferably, thematerial and design of at least a portion of module (100) are such thathousing (102) may be produced by vacuum forming or molding techniques.

Where discrete cover (112) and base (114) portions are used, they may bemechanically secured to one another through bolt holes (120). In such aninstance, a gasket or caulking may be employed to seal the periphery ofhousing (102).

Providing a separable cover (112) and base (114) or heat exchangeelement (106) provide advantageous access to clean module (100) afteruse. However, it is contemplated that the top and bottom portions of themodule may be fused together, for instance, by ultrasonic welding,chemical bonding or otherwise. Also, as noted above, it is contemplatedthat housing (102) may be provided in a single piece.

Regardless of the construction, sizing or overall appearance of housing(102), it defines a portion of chamber (104). A heat exchange surface(122) for delivering or accepting a thermal load from a user alsodefines a portion of chamber (104). A user may directly contact heatexchange surface (122). Alternately, a user may wear a glove or sock ortake other prophylactic measures. Heat exchange surface (122) may beprovided by a member separate from heat exchange member (106) such as byan intermediate layer of foil, metalized Mylar or another material.

Heat exchange element (106) is preferably made of aluminum or anotherhigh thermally-conductive material. It may be in communication with aPeltier device, a desiccant cooling device or an endothermic orexothermic chemical reaction to provide a temperature variance. Morepreferably, however, heat exchange member (106) is in communication withat an inlet and an outlet (124) to accommodate a flow of perfusionliquid behind heat exchange surface (122). Chilled or heated water maybe used to maintain the contact surface of the element at a desiredtemperature. Optimally, perfusion fluid is run through a series ofswitchbacks in cavity (126) between element (106) and base (114).

A rear portion of housing (102) and heat exchange member (106) may beprovided by plate (128). As depicted, this portion may include provisionfor inlet and outlet (124) to heat exchange cavity (126) and an opening(130) to chamber (104). A preferred manner of constructing seal (108) isdisclosed in connection with plate (128).

Views detailing preferred geometric aspects of seal (108) are shown inFIGS. 4, 5 and 6. FIG. 4 shows an end-on view of seal (108). Preferably,at least portions of seal (108) are ovalized in form. An ellipticalshape may be preferred. A circular shape may also be used. Still, ashape having a major axis (132) and a minor axis (134) will bepreferred, at least for the waist opening (136) of seal (108). Anovalized shape approximately corresponds to the shape of the wrist orforearm of a user. A shape having a major axis (132) and a minor axis(134) will also be preferred at chamber opening (130) and seal opening(138). This will assist in providing clearance for hand entry and exitof module (100). It will also simplify the construction of seal webbing(140).

Whether or not ovalized features are utilized for seal (108), it will beshaped roughly like an hourglass. Seal (108) will most closely resemblean hourglass if openings (130), (136) and (138) are circular. Whenovalization is applied, different projected views of seal (108)—such asviewed in FIG. 5, for the section taken along line A-A and in FIG. 6 forthe section taken along line B-B—display an hourglass shape.

Of course, the shapes depicted may be characterized as other than“hourglass” forms. For instance, profiles of seal (108) may be viewed ashyperbolic or parabolic. Further, simple radiused or semi-circularcross-sections may be utilized in producing seal (108). Furtherstraightened sections may be used, especially, between the openings(130) and (138) and waist (136).

Whatever the case, a two-sided seal with outside openings of a greatersize than that of the inside opening is to be used in module (100). Thisgeometry provides for ramps or transition sections for appendage entryand exit. These features assist in stretching the seal interface orwaist (136) sufficiently wide to pass a hand or foot both for insertioninto and removal from module (100).

Material selection is important in providing such a seal. Clearly, thematerial must be able to stretch. Further, it should provide asubstantial barrier to air flow. To meet each of these criteria, aurethane-backed lycra available from Malden Mills (Malden, Mass.) hasproven effective. Still, it is contemplated that other materials may beused. The material (or materials) selected for webbing (140) preferablyhas a finish that does not grip onto a user so as to complicate entryand exit from module (100). The urethane skin of the referenced materialhas a satin finish. This decreases friction with the skin and hair of auser.

In addition to providing sufficient stretch, the seal webbing materialshould also have sufficient strength to avoid being drawn too far intocavity (104) upon the application of vacuum. When in use, the openconstruction of seal (108) will result in cavity-side webbing materialexposed to partial vacuum within chamber (104) to be forced by ambientpressure inward. This self-inflation phenomena observed for thechamber-side of the seal may be of assistance in providing seal patencywith a user. However, if too much material bows inward, it will resultin an uncomfortable or disconcerting displacement of the user's hand orfoot into the device. Accordingly, with proper material choice, the sideof seal (108) opposite chamber (104) provides not only a transitionsection for entry and exit, but also a stabilizing feature for sealposition.

Seal (108) is preferably formed by a sleeve made by stitching two piecesof webbing material (140) together where they are shown broken apart inthe exploded view of FIG. 3. By constructing the sleeve from two or morepieces, complex shapes can be easily produced. To secure the sleevewebbing (140) in place to form seal (108), it is folded over rings (142)at each end as variously depicted. Then the cavity-side ring and webbingis captured in opening (130) of plate (128). The opposite side of sealwebbing (140) is captured between outer ring (142) and retainer member(144). Standoffs (146) or equivalent structure space plate (128) andring retainer (144) apart to define the overall length of seal (108). Ofcourse, the length of the standoffs or seal may be varied as well as theother parameters of seal (108) that effect fit.

In this respect, it is noted that it may be desirable to provide alonger overall seal in some instances. Increasing overall lengthprovides further design flexibility with seal shape. This may be besttaken advantage of by increasing the length of waist (134) to providegreater seal surface contact with a user. This may beneficially reduceany undesirable constricting effects. Furthermore, it is to beappreciated that the nature of the material used for the seal webbing(140) may be advantageously varied. While the noted lycra-based materialis isotropic in nature, an anisotropic material or effect may bepreferred for the webbing. This is to say that greater radial expansionof the sleeve may be desirable, whereas longitudinal compliance may notbe. By reducing compliance along the axis of the sleeve relative to aradial component, it will tend to be drawn into chamber (104) to alesser degree upon the application of vacuum. For a very high-stretchmaterial, this will allow for smaller seal openings to fit the samepopulation (since they can still stretch webbing (140) radially and haveit return sufficiently to form a desired seal), without forfeiting thefull set of advantages that the two-sided seal described offers.

Such an anisotropic effect may be achieved in a number of ways. It maybe accomplished by providing longitudinal reinforcement member(s)associated with the webbing. They may be incorporated through braidingtechniques, by bonding/affixing stiffener(s) to the sleeve surface or byother means as would be apparent to one with skill in the art.

Regardless of the particulars of seal construction and whether it isutilized to provide a “hard” or “soft” user interface, the dual-sidedseal disclosed provides a superior manner of carrying out themethodology noted above. Though a “soft” two-sided seal as shown in thefigures is preferred for its elegance in approach and proveneffectiveness, a “hard” or more complex “soft” seal approach mightsometimes be desired.

In order to utilize the dual-sided seal in a “hard” approach,supplemental forcing means may be provided to apply pressure around sealwaist (134). Mechanical means such as at least one of a strap, belt orcinch may be used. Alternately an inflatable cuff or bladder portionsaround the periphery of the seal may be employed. While the systemcomplexity will increase due to provision for providing the supplementalpressure and controlling it by either automated or manual means, certainpotential advantages arise. It may enable a single-evacuation procedurefor chamber (104) rather than relying on constant or periodic vacuumreplenishment. It may also provide greater design flexibility for seal(108). Particularly, by providing another variable to utilize in designdecisions, a lesser emphasis may be placed on webbing material choice oropening sizing since the supplemental forcing capacity may be used toshape the seal as desired in use. Further, it may enable fitting seal(108) to a wider range of a populous for a given configuration of hardelements, such as those that make-up seal frame (110).

Supplemental forcing or seal shaping may also be used to produce a morecomplex “soft” seal than that described above. As with a “hard” sealapproach, this would open design and fit possibilities. Forcing or sealshaping parameters may, again, be controlled manually or automatically.Except, in a complex “soft” seal, the control of pressure applied towaist (134) is gauged to provide a compliant feel or fit. Since theapplication of pressure on the seal interface with the user may be theonly difference between a complex “soft” seal approach and a “hard” sealapproach utilizing the dual-sided configuration, the same apparatus maybe configured to function in either manner, for instance, by providingvariable pressure control.

The negative pressure means and the warm medium contact means, describedabove, are typically actuatable, i.e., turned on and off, by a controlmeans which controls actuation of the negative pressure means and thewarming medium in response to whether thermal energy input is requiredto maintain the core body temperature of the mammal. The control meansis generally a processing means that is capable of taking output datafrom the detecting means, i.e., data with respect to whether or notthermal energy input is required or not to maintain the core bodytemperature of the mammal, processing the data to determine whether ornot the negative pressure means/warming means should be actuated or notand then actuating these components of the device accordingly

Utility

As demonstrated above, the subject methods provide a means formaintaining the core body temperature of a mammal at a substantiallyconstant value under cold conditions. The subject methods are able tomaintain the core body temperature of a mammal under cold conditions byintroducing thermal energy or heat into the core body of a mammal inresponse to a detection of a requirement to do so in order to avoid atemperature drop in the core body temperature of a mammal. As such, thesubject methods are suitable for use in a variety of differentapplications, where representative applications include maintaining thecore body temperature of mammal at a substantially constant value undercold conditions for extended periods of time. As such, the subjectmethods and devices allow a mammal to remain in a cold environment foran enhanced period of time as compared to a control, e.g., an equallyequipped individual without the subject methods and devices, withoutadverse effects on the individual. By enhanced period of time is meantan increase of at least about 1.2 fold, usually at least about 1.5 foldand more usually at least about 2.0 fold. Adverse effects that can beavoided using the subject methods include: impairment of physicalability, impairment of mental ability, etc. Accordingly, the subjectmethods and devices find use in applications where it is desirable forthe individual to remain under cold conditions for extended periods oftime, e.g., where individuals are working under cold conditions, e.g.,in cold ocean water, in cold climates, etc.

It is evident from the above results and discussion that the subjectinvention provides a convenient means for maintaining the core bodytemperature of a mammal under cold conditions. Specifically, the subjectinvention is a non-invasive, simple to perform method and easy to usedevice which conveniently maintains the core body temperature of themammal in a manner that is substantially non-interfering to the mammal,i.e., in a manner that is well tolerated and substantially not noticedby the mammal. Benefits of the subject methods and devices include theability to dramatically extend the period of time that the mammal can beexposed to cold conditions without experiencing adverse effects,including physical and/or mental impairment. As such, the subjectmethods and devices find use in a variety of diverse applications,including applications in which they are employed to improve workerhealth and product under cold conditions, e.g., underwater and coldclimate work environments. In view of the above discussion and results,it is readily apparent that the subject invention represents asignificant contribution to the art.

All publications and patent applications cited in this specification areherein incorporated by reference as if each individual publication orpatent application were specifically and individually indicated to beincorporated by reference. The citation of any publication is for itsdisclosure prior to the filing date and should not be construed as anadmission that the present invention is not entitled to antedate suchpublication by virtue of prior invention.

Although the foregoing invention has been described in some detail byway of illustration and example for purposes of clarity ofunderstanding, it is readily apparent to those of ordinary skill in theart in light of the teachings of this invention that certain changes andmodifications may be made thereto without departing from the spirit orscope of the appended claims.

1. A method for preventing a change in the core body temperature of amammal under cold conditions, said method comprising: (a) detecting arequirement for thermal energy input in said mammal; and (b) contactinga surface of a portion of said mammal in response to the presence ofsaid requirement with a warm temperature medium under negative pressureconditions for a period of time sufficient to introduce thermal energyinto the core body of said mammal; whereby the core body temperature ofsaid mammal is prevented from changing under said cold conditions. 2.The method according to claim 1, wherein said requirement is detected bydetecting the presence of a thermoregulatory error in said mammal. 3.The method according to claim 1, wherein said thermoregulatory error isdetected by detecting the presence of vasoconstriction in said mammal.4. The method according to claim 1, wherein said method furthercomprises enclosing said portion of said mammal in a sealed enclosure toproduce an enclosed portion of said mammal.
 5. The method according toclaim 1, wherein said method is a method of maintaining said core bodytemperature of said mammal substantially constant for a temporalduration of at least about 60 min and said method comprises performingsteps (a) and (b) at least twice during said temporal duration.
 6. Themethod according to claim 1, wherein said portion of said mammal is alimb or a portion thereof.
 7. The method according to claim 6, whereinsaid limb is selected from the group consisting of an arm and a leg. 8.The method according to claim 4, wherein said sealed enclosure has apressure ranging from about −20 to −80 mm Hg.
 9. The method according toclaim 1, wherein said warm temperature medium has a temperature rangingfrom about 44 to 48° C.
 10. The method according to claim 1, whereinsaid period of time ranges from about 1 to 600 min.
 11. The methodaccording to claim 1, wherein said mammal is a human.
 12. A method formaintaining the core body temperature of a mammal substantially constantfor a temporal duration of at least about 60 min under cold conditions,said method comprising: (a) monitoring said mammal during said temporalduration for the presence of a thermoregulatory error; and (b)contacting a surface of an enclosed portion of said mammal in responseto the presence of said thermoregulatory error with a warm temperaturemedium under negative pressure conditions for a period of timesufficient to introduce thermal energy into the core body of saidmammal; whereby the core body temperature of said mammal is maintainedsubstantially constant during said temporal duration. 13-21. (canceled)22. A device for introducing thermal energy into the core body of amammal under cold conditions, said device comprising: (a) a means fordetecting a requirement for thermal energy input in said mammal; (b) asealable enclosure for enclosing a portion of said mammal; (c) a meansfor producing negative pressure conditions in said sealable enclosure;and (d) a warming means for producing a warm temperature medium in saidsealable enclosure.
 23. The device according to claim 22, wherein saidportion of said mammal is a limb or portion thereof.
 24. The deviceaccording to claim 23, wherein said limb is selected from the groupconsisting of an arm and a leg.
 25. The device according to claim 22,wherein said means for detecting a requirement for thermal energy inputin said mammal is a means for detecting a thermoregulatory error in saidmammal.
 26. The device according to claim 25, wherein said means fordetecting a requirement for thermal energy input in said mammal is avasoconstriction detecting means.
 27. The device according to claim 22,wherein said means for producing a negative pressure in said sealableenclosure is capable of producing a negative pressure ranging from about−20 to −80 mm Hg.
 28. The device according to claim 22, wherein saidmammal is a human.
 29. The device according to claim 22, wherein saidsealable enclosure has a configuration selected from the groupconsisting of a sleeve, glove and boot.